1. Field of the invention.
This invention relates to an improved end seal for an electrical conduit and method for installing the end seal. More particularly, it relates to a low cost end seal which may be provided as a standardized fitting for plastic electrical conduits which may be reliably installed under field conditions by contractor or utility personnel without specialized training.
2. Description of the Prior Art
The necessity for providing an end seal for electrical cables or conduits to prevent moisture and gases from entering the cables or conduits from their ends has long been recognized. For example, U.S. Pat. Nos. 1,109,726 and 1,115,447 disclose end seals particularly adapted for a lead sheath cable employed at that time. A further refinement in an end seal for such lead sheath cable is found in U.S. Pat. No. 2,247,671.
Somewhat similar considerations apply when it is desired to splice cable together. Various housing structures are disclosed for this purpose, as disclosed in, for example, U.S. Pat. No. 3,569,608 and U.S. Pat. No. 3,823,254. In particular, U.S. Pat. No. 3,569,608 discloses the concept of compressing an elastomeric member in a cable splicing housing in order to form a reliable seal. U.S. Pat. No. 3,655,907 discloses the application of that approach to a conduit cable end seal. Various end seals are commercially available which employ the compression of a rubber or similar member to produce the seal. However, such end seals consist of at least several separate parts which must be carefully installed, and they are sufficiently expensive so that they are usually only employed for specialized applications.
At the present time, the use of polyvinyl chloride (PVC) plastic pipe for electrical conduits, particularly in residental hook-ups, has achieved wide usage. As underground electrical distribution lines become more popular the usage of these conduits should become even more widespread. Although the compressed resilient member type of end seal can be employed with PVC conduit, the high cost and difficulty of installing such seal has meant that PVC conduits are usually installed with no end seals. A need therefore remains for a conduit end seal especially adapted for use with PVC and other plastic pipe conduit.